More ships arrived at their destination ports behind schedule in the fourth quarter, according to the latest Container Shipper Insight report from Drewry Shipping Consultants.

Of nearly 1,600 ships tracked in the three months ending Dec. 31, only 53 percent arrived either on the scheduled day of arrival or a day prior, Drewry said. That was down 7 percentage points from the reliability rate in the first three quarters of 2009 as well as falling below the historic average, which now stands at 55 percent.

The increase in unreliability coincides with an increase in the practice of slow steaming. While ships might have been expected to arrive a bit later because they are moving slower, their scheduling should not be more difficult.